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CN-122029392-A - Coating section of continuous production line

CN122029392ACN 122029392 ACN122029392 ACN 122029392ACN-122029392-A

Abstract

The invention relates to a method for cooling a metal strip (2) in a coating section (1) of a continuous production line for processing the strip, which strip is dried in a heating section (300) and then pre-coated with a coating comprising a dry extract and a diluent before being cooled in a cooling section (600), characterized in that the cooling is carried out successively in a primary cooler (400) and then in a secondary cooler (500), wherein the strip is cooled in the primary cooler by convection by means of a gas blown onto the strip, the temperature of which gas is selected so as to maintain a temperature in the primary cooler that is higher than the condensation temperature of the diluent.

Inventors

  • Cyril Craveruras

Assignees

  • 法孚斯坦因公司

Dates

Publication Date
20260512
Application Date
20240925
Priority Date
20230927

Claims (12)

  1. 1. Method for cooling a metal strip (2) in a coating section (1) of a continuous production line for processing the strip, the strip being dried in a heating section (300) and then pre-coated with a coating comprising a dry extract and a diluent before being cooled in a cooling section (600), characterized in that the cooling is performed successively in a primary cooler (400) and then in a secondary cooler (500), wherein the strip is cooled in the primary cooler by convection by means of a gas blown onto the strip, the temperature of the gas being selected so as to maintain a temperature in the primary cooler that is higher than the condensation temperature of the diluent.
  2. 2. The method according to the preceding claim, wherein the strip is cooled in the secondary cooler (500) by means of a fluid having a temperature lower than the temperature of the gas blown onto the strip in the primary cooler (400).
  3. 3. The method according to the preceding claim, wherein the strip is cooled in the primary cooler (400) to a temperature between 130 ℃ and 170 ℃.
  4. 4. The method according to one of the preceding claims, wherein air preheated to a temperature above the condensation temperature of the diluent in the primary cooler (400) is injected into the primary cooler via an injection line (410), and gas comprising the injected air and diluent vapour is extracted from the primary cooler via an extraction line (416, 330).
  5. 5. The method according to the preceding claim, wherein the gas present in the primary cooler (400) is extracted via the heating section (300) through the extraction line (330) connected to the heating section.
  6. 6. The method according to one of claims 4 or 5, wherein the gas blown onto the strip in the primary cooler (400) is extracted from the primary cooler (400) and recirculated via a recirculation circuit (403), the temperature of the gas blown onto the strip being adjusted by injecting a controlled flow of fresh air into the recirculation circuit (403) via an air inlet (405).
  7. 7. A coating section (1) of a continuous production line for processing metal strips (2), comprising an application section (100) for coating the strips with a coating comprising a drying extract and a diluent, a heating section (300) for drying the coating, and a cooling section (600), characterized in that the cooling section comprises a primary cooler (400) in which the strips are cooled by convection by means of a gas blown onto the strips, the temperature of the gas being selected so as to maintain a temperature in the primary cooler above the condensation temperature of the diluent, followed by a secondary cooler (500) in which the strips are cooled by means of a fluid, the temperature of the fluid being lower than the temperature of the gas blown onto the strips in the primary cooler.
  8. 8. The coating section (1) according to the preceding claim, wherein the primary cooler (400) comprises a blowing chamber (401) arranged opposite the strip and supplied with cooling gas by a circuit (403) for recirculating the gas present in the primary cooler (400), which is connected to an injection line (410) for controlled injection of a flow of preheated air into the primary cooler.
  9. 9. The coating section (1) according to one of claims 7 or 8, wherein a recirculation circuit (403) comprises an air inlet (405) allowing a controlled flow of fresh air to be injected into the recirculation circuit to adjust the temperature of the gas supplied to the blowing chamber (401).
  10. 10. The coating section (1) according to one of claims 7 to 9, wherein the primary cooler (400) is connected to the heating section (300), the coating section further comprising an extraction line (330) connected to the heating section (300), the extraction line being adapted to extract gas from the primary cooler (400) via the heating section (300).
  11. 11. The coating section (1) according to one of claims 7 to 10, further comprising an airlock (200) arranged at the inlet of the heating section (300).
  12. 12. The coating section (1) according to one of claims 7 to 11, further comprising an extraction line (416) connected to the primary cooler (400) for extracting the gas present in the primary cooler.

Description

Coating section of continuous production line Names of the technical fields in question The present invention relates to a continuous production line for treating metal strips, and more particularly to painting or varnishing sections, whether these sections are vertical or horizontal, that is to say whether the strip runs vertically or horizontally within the sections. The invention is particularly applicable to coated sections of carbon steel, silicon steel or aluminum strips. Hereinafter we will use the term "coating" to refer to any type of coating, whether it is paint, varnish or any other type. Technical problems to be solved by the invention The coated section consists of: A coating application zone on the strip, A coating drying/polymerization zone, Strip cooling zone. In the application zone, the coating is applied to the strip using a roll coating process. A calibrated coating thickness is applied to the strip. The coating generally consists of: drying the extract (pigment, binder, etc.), One or more diluents (solvent, water or solvent + water). Once the coating has been applied to the strip, it must be dried, that is to say, all the diluent contained in the coating must be evaporated, so that only the dried extract remains on the strip. In the following we will assume that the coating comprises a single diluent, but this does not limit the scope of the patent to this case only, as the invention is equally applicable to coatings comprising a single diluent or several diluents. The temperature that the strip must reach in the heating section is referred to as the Peak Metal Temperature (PMT). The temperature varies depending on the nature of the coating but is typically between 200 ℃ and 300 ℃. The strip is heated in the heating section by convection, radiation (infrared) or induction. The ambient temperature in the heating section must be maintained above the condensation temperature of the diluent in the coating to prevent the diluent from recondensing on the walls of the heating section that are in contact with the cold surface once evaporated from the substrate. The diluent evaporation temperature is about 100 ℃ for water and between 150 ℃ and 250 ℃ for solvent. The heating section may consist of a heating zone alone or in combination with a temperature maintenance zone. The drying zone or holding zone is maintained under negative pressure by air extraction to evacuate the evaporated solvent. If the diluent is water, the extract is sent directly to the outside of the building, or if the diluent is a solvent, the extract is sent to a treatment system, and the treated air is then released to the atmosphere. After drying, the strips are cooled in a cooling section. In most cases, water spray cooling is used immediately after leaving the heating section. In some cases, the strip cannot be cooled directly with water for process reasons. In this case, the cooling is carried out entirely or partly by means of air. This involves blowing cool air onto the sheet to cool the sheet. We have found such an air cooled configuration, for example: in certain sections of the aluminum strip coating, in which sections the water cooling is too severe and flatness defects are created on the strip, On the painted section of the steel strip to which the plastic film is applied after painting, And (3) coating the section on the silicon wafer material. In the coating section, certain problems occur when the strip is cooled not by spraying water but by blowing cold air. In fact, the water cooling quickly cools the strip and almost immediately stops emissions from the substrate. In the case of air cooling, the cooling is slower and the strip continues to emanate. The emissions are mainly solvents and resins. These emissions (fugitive emissions) contaminate the cooling zone, causing environmental problems. These effluents are usually captured at most and rarely disposed of. They are typically simply released into the atmosphere. Furthermore, since these emissions occur in the cold zone, there is a problem of condensation of solvent/resin in the cooling zone and in the collecting ducts, which causes safety problems since these condensates are highly flammable. The object of the present invention is to overcome these problems. Disclosure of Invention According to a first aspect of the invention, a method is proposed for cooling a metal strip in a coating section of a continuous production line for processing the strip, the strip being dried in a heating section and then pre-coated with a coating comprising a dried extract and a diluent before cooling in a cooling section, characterized in that the cooling is performed successively in a primary cooler in which the strip is cooled by convection by means of a gas blown onto the strip, the temperature of the gas being selected so as to maintain a temperature in the primary cooler above the condensation temperature of the diluent. The temperature of the gas blown onto the strip is